9  R: Functions

9.1 Defining a function

Functions in R are defined using the keyword function(). All the statements within a function are enclosed with {} braces. Look at the function defined below. It takes an integer as an argument, and prints whether the integer is odd or even.

odd_even<-function(intgr)
{
  if(intgr%%2==0)
  {
    print("even")}else{
      print("odd")
  }
}

odd_even(3)

[1] "odd"

9.1.1 Practice exercise

Write a function that returns all prime numbers between \(a\) and \(b\), where \(a\) and \(b\) are parameters of the function.

prime<-function(a,b)
{
  prime_numbers<-c()
  for(number in a:b)
  {
    prime = 1
    for(factor in 2:(number-1))
    {
      if(number%%factor==0){
        prime = 0
      }
    }
    if(prime==1){prime_numbers<-c(prime_numbers,number)}
  }
  return(prime_numbers)
}
prime(40,60)

[1] 41 43 47 53 59